They choose their best horse that they thing will perform the best for the task on hand.
yes you can
you start to canter
Its ok if all the horses are not being ridden, but they will have to be ridden later.
most horses probably travel in style to the olympics: in airplanes made for them, or in horse trailers
you stay still or walking.
There have been many riders killed by horses.
I stay still or walking
17 years and 4 days
You start to canter in the indoor ring.
There are horse events in the Olympics: Show-jumping But a so called "Horse Olympics" where horses participate in dressage,show-jumping, cross country etc are called gymkhanas.
horse shows were inveted for riders to show their and their horses skills and acheive higher levels
Horse riders usually say 'back', or 'back boy/girl', if you are on the ground, but if you are riding, then you have to gently pull the reigns alternately, whilst kicking gently, but firmly. Most horses will do this, but you have to be careful, because it can confuse some young horses.